Known display devices have backlights arranged to illuminate pixels of the display device. The pixels operate as optical switches to obscure a varying proportion of light from the backlight in order to produce display effects ranging from a darkest display effect, which may be intended to correspond with a complete obstruction of light from the backlight, to a lightest display effect, which may correspond with a minimal obstruction of light from the backlight. Backlights come in various forms, including globally-adjusted backlights, in which the luminance of the backlight is adjusted equally across the entire display, one dimensional locally-adjusted backlights in which the luminance of the backlight may be adjusted differently along strip-like regions arranged side by side along one dimension of the display, and two dimensional locally-adjusted backlights in which the luminance of the backlight may be adjusted differently in square or rectangular regions arranged in a two dimensional array across the display.
Known display devices suffer from light leakage. This means that the pixels are unable to completely obscure light from the backlight even for the darkest display effect. In other words, light may leak from the backlight and be visible to an observer even in an off state of the display device. Dark display effects may therefore be lighter than desired or intended, leading to a corresponding reduction in contrast of the display device.
It is known to reduce light leakage of a display device by locally dimming the backlight for dark image regions. However, a locally dimmed backlight as described above is relatively complex and many devices do not have local dimming. Even if local dimming is available, the size and configuration of the dimmable regions is unlikely to correspond with the size and shape of the light and dark regions of an image.
It is desired to provide a method of controlling display of image data representing an image on a display device to provide an improved display quality.